Magnetic resonance imaging (MRI) is the method of choice for noninvasive diagnosis of soft tissue disease in humans, and has wide applications in cardiovascular diseases. Fast gradient technology has made high-resolution 3D imaging possible, including magnetic resonance angiography (MRA) of coronary and pulmonary arteries. However, the acquisition time for high quality, high resolution data is on the order of minutes. Artifacts from physiological motion occurring during data acquisition, such as respiration and cardiac contraction, degrade image quality and result in blurring or ghosting.
Industry responded by developing methods to suppress the artifacts caused by physiological motion. One suppression approach is the real-time navigator method, which monitors respiration and controls data acquisition accordingly in real-time. Most current navigator techniques are based on gating and they reconstruct images only using data acquired when motion is in a specified window. In these navigator techniques, a motion tolerance window (e.g., gating window) is specified and only the data that is within the specified window is used to construct images. Effective motion suppression requires a small gating window that leads to a long scan time, resulting in inefficiencies. Typically, a single image volume at a window near the most likely motion position, as indicated by the peak of the subject's motion histogram, is taken as represented in FIG. 9. Currently, one of the most efficient methods available is the phase ordering with automatic window selection method (i.e. PAWS), which is optimized against variation in the subject's respiration pattern. In the PAWS method, a fraction of the total scan time corresponding to a small gating window is used for image acquisition. Data at other motion levels are not useable. As a result, scan time is wasted when the subject's position is outside the gating window.